Processes used in the production of frozen foods are highly specialized and specifically designed to optimize the appeal and sales value of a particular product. Heat transfer may be accomplished by direct contact of a food product or packaged food product with a refrigerant or by contact with a refrigerated gas or liquid. The process used for a particular food product depends to a large extent on the type of product, the water content of the product and the manner in which the food product is to be delivered to and prepared by a consumer.
Frozen meat and fish products are generally pre-packaged before freezing to reduce water loss from the product during the freezing process and protect against freezer burn.
Relatively large food products, such as green peas, string beans, and the like, are generally pre-packaged and frozen by a blast of refrigerated gas. Any water that is removed from the product during the freezing process is retained in the package and the individual food particles are often frozen together in a solid mass. However, such a condition of this type of frozen food product is not a matter of customer concern since these products are usually heated in preparation for use and the individual food particles separate during such preparation.
Prior art processes utilize various means including belts and trays as well as fluidized beds for the conveyance of the food products being frozen in such a manner that the products will be exposed to the freezing medium. U.S. Pat. No. 3,169,381 discloses an apparatus and method for freezing solid food particles by creating a fluidized bed by introducing such particles to a vessel and forcing refrigerated gas upwardly through the particles which are then moved in the direction of a vessel outlet by continuously introducing the feed product to create a fluid head at one end of the vessel. U.S. Pat. No. 3,865,965 discloses a method of cooling previously heated or "blanched" vegetables which utilizes a vibrating or reciprocating fluidized bed frame prior to subjecting the vegetables to a freezing operation. United Kingdom Patent Application GB No. 2039015 discloses a two-stage freezing process which includes a reciprocating and pivoting conveyor for delivering food products having a relatively high water content to a fluid bed which constitutes the first or preliminary freezing stage.
Thus many various approaches have been developed in the prior art to accommodate specific problems encountered with various types of food products and the manner in which they will be prepared. Basic considerations such as, equipment costs, economics of obtaining satisfactory heat transfer and the cost of maintaining a sanitary operation are important factors in the process selection for each type of food product.
Customer acceptance of various frozen dairy products depends greatly not only on the specific composition of the product but also on the nature of the frozen water content and on its distribution in the product. For example, if ice cream compositions are not adequately mixed by a shearing action during the freezing process, water tends to separate from the mixture and form large unpalatable crystals which are generally undesirable to a consumer. Rapid freezing tends to form small crystals of water in the frozen product.
Cheese is another dairy product, at least 30% water by weight and usually higher, which poses unique problems for specific applications of the food product. Cheese of the type used on pizzas as well as other pasta products is usually prepared in granular form. Fresh cheeses have long been preferred in the preparation of pizza both from the standpoint of good appearance and physical quality of the finished baked product. However, fresh cheese granules, particularly those comprising mozzarella cheese or a blend of mozzarella cheese with other cheese, tend to stick together making it difficult to evenly spread the cheese granules on the pizza during preparation for baking and this detracts from the appearance and quality of the baked product.
With the growing popularity of pizza, both freshly prepared and frozen pizzas, a need has been recognized to produce improved free flowing frozen particulate cheese products. Specifically, there is a need to produce free flowing granules of cheese that can be readily handled in the process of making the pizzas and of such a quality that they can be baked on the pizzas in a frozen or partially frozen condition while obtaining as good a quality of baked pizza product as when fresh or fully thawed granule cheese is used. The desirability and use of frozen particulate granules of cheese in the preparation of pizza are described in U.S. Pat. No. 4,753,815. The use of commercially available equipment for freezing "comminuted cheese" of the type sold for individual quick freezing of food products is also disclosed in that patent. However, notwithstanding the availability of prior art equipment for individual quick freezing of other types of food products, there is a recognized need for improved methods for producing individual free flowing particulate granules of cheese including mozzarella cheese of the type used in the preparation of pizzas.
The present invention provides an improved process and apparatus for the manufacture of particulate frozen food products and, more specifically, the manufacture of particulate frozen food products having a high water content.
One object of the present invention is to provide an improved process for producing frozen cheese granules for use in making pizza products.
A further object of the present invention is to provide a process for producing frozen cheese granules of the kind useful for making pizzas which process maintains both the moisture content and the nature of the moisture contained in the fresh cheese granules before freezing.
It is a still further object to provide a process for producing particulate frozen granules of high water content food products wherein substantially all feed material is recovered as a marketable product.
It is a still further object of the present invention to provide process equipment for the manufacture of particulate granules of high water content food products that is uniquely capable of being cleaned in place and also meets food grade standards for producing dairy products.
It is a still further object of the present invention to provide a process for producing frozen cheese particles having product performance properties, when used in baked goods, that are essentially equivalent to those properties obtained as a result of using fresh cheese granules.